Preparation process of aluminum paste with controllable particle size

Abstract

The invention discloses an aluminum paste preparation process capable of accurately controlling the particle size, which comprises the following steps: pretreating aluminum ingots or aluminum scraps with the purity of not less than 99.5%, then preparing aluminum powder in an inert gas environment by adopting a mechanical grinding method, and accurately regulating and controlling the particle size by controlling the ball-to-material ratio and the grinding time; carrying out surface treatment on the aluminum powder; finally, a flatting agent, an anti-settling agent and the like are added for tempering and stabilizing, the viscosity is adjusted to 10-50 Pa.s, and the solid content is adjusted to 40%-60%; by optimizing each preparation link, accurate regulation and control of the particle size of the aluminum paste are achieved, meanwhile, the dispersibility, corrosion resistance, storage stability and other performance of the aluminum paste are improved, and energy consumption and safety risks in the production process are reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of metal pigment preparation, and in particular to a process for preparing aluminum-silver paste with precisely controllable particle size. Background Art

[0002] As an important metallic pigment, aluminum paste is widely used in coatings, inks, plastics and other fields. Its performance directly affects the decorativeness and functionality of the final product. Among them, the particle size of aluminum powder is one of the key factors that determine the performance of aluminum paste. Aluminum pastes of different particle sizes are suitable for different application scenarios. At present, in the preparation process of aluminum paste, mechanical grinding is a commonly used method for preparing aluminum powder. However, this method has problems such as high energy consumption and easy introduction of impurities, and the accuracy of particle size control is limited. In the overall preparation process of aluminum paste, the effect of raw material pretreatment, the degree of mixing and dispersion, tempering and stabilization treatment, and classification method will all affect the performance of the final product. The existing technology still needs to be further improved and perfected in terms of precise control of particle size, optimization of product performance and production safety. It is urgent to develop an aluminum paste preparation process that can achieve precise control of particle size, improve product quality and be safe and environmentally friendly. Summary of the Invention

[0003] In response to the shortcomings of the existing technology, the present invention provides an aluminum-silver paste preparation process with precisely controlled particle size. By optimizing each preparation link, the precise regulation of the aluminum-silver paste particle size is achieved, while the dispersibility, corrosion resistance, storage stability and other properties of the aluminum-silver paste are improved, thereby reducing energy consumption and safety risks in the production process.

[0004] To achieve the above object, the present invention provides the following technical solutions:

[0005] A process for preparing aluminum-silver paste with controllable particle size comprises the following steps:

[0006] (1) Raw material pretreatment

[0007] ① Select aluminum ingots or aluminum chips with a purity of not less than 99.5% as the raw material for preparing aluminum powder. Place the raw material in a sodium hydroxide solution with a concentration of 5% to 10%, soak it at 40-60℃ for 10 to 20 minutes to remove surface oxides and impurities, then rinse it repeatedly with deionized water until it is neutral, and dry it for later use;

[0008] ② Place the pretreated aluminum powder in a reactor, add 0.3% to 3% of the coating agent by weight of the aluminum powder, and add an appropriate amount of organic solvent. React at 60-80°C and a stirring speed of 300-500 rpm for 1-3 hours to evenly coat the coating agent on the surface of the aluminum powder.

[0009] (2) Aluminum powder preparation

[0010] ①Put the pretreated aluminum raw materials into the jaw crusher for preliminary crushing, so that the particle size of the aluminum raw materials reaches 1-5mm;

[0011] ② The coarsely crushed aluminum particles are transferred to a ball mill and ground under inert gas protection. The ball-to-material ratio in the ball mill is controlled at (5-15):1, and the grinding medium is zirconia balls with a diameter of 3-8 mm. During the grinding process, the speed of the ball mill is controlled at 200-400 rpm, and the grinding time is adjusted according to the target particle size.

[0012] ③ Use an airflow separator to classify the ground aluminum powder. The airflow speed of the airflow separator is 10-30m / s and the separation temperature is 20-40℃. Aluminum powders of different particle sizes are separated and aluminum powders that meet the target particle size requirements are collected for later use.

[0013] (3) Mixing and dispersion

[0014] ① Add the organic solvent and the resin in a mass ratio of (3-7): (7-3) into a planetary mixer and mix them at a stirring speed of 200-400 rpm for 1-2 hours to fully dissolve and mix the organic solvent and the resin;

[0015] ② Add the aluminum powder prepared in step (2) to the mixed solvent resin system, the amount of aluminum powder added is 20% to 40% of the total mass of the system, and at the same time add 0.5% to 2% of the total mass of the BYK series dispersant; then transfer the mixture to a sand mill, and perform high-speed shear dispersion under the conditions of a grinding pressure of 0.3-0.8 MPa and a grinding medium of glass beads with a diameter of 0.3-0.8 mm for 2-4 hours to fully disperse the aluminum powder in the system and grind until the fineness of the aluminum-silver paste reaches <20 μm.

[0016] Preferably, in step (1)②, the coating agent is stearic acid or a silane coupling agent.

[0017] Preferably, in step (2)②, when the target particle size is 1-5 μm, the grinding time is 12-24 hours; when the target particle size is 5-10 μm, the grinding time is 6-12 hours; when the target particle size is 10-20 μm, the grinding time is 3-6 hours.

[0018] Preferably, in step (3)①, the organic solvent is xylene or butyl acetate.

[0019] Preferably, in step (3)①, the resin is an alkyd resin or an acrylic resin.

[0020] Preferably, in step (3)②, a hydrophilic auxiliary agent is added as needed, and the hydrophilic auxiliary agent is polyethylene glycol, and the addition amount is 0% to 2% of the total mass of the system.

[0021] Preferably, the aluminum-silver paste prepared in step (3) can be further tempered and stabilized by the following steps:

[0022] ① Add 0.2% to 1% of the total mass of the leveling agent and 0.5% to 2% of the anti-settling agent to the dispersed aluminum-silver paste, and stir at a stirring speed of 100-300 rpm for 0.5-1 hour;

[0023] ② Adjustment of viscosity and solid content: According to the application requirements of spraying or printing, adjust the viscosity of aluminum-silver paste to 10-50 Pa·s and the solid content to 40%-60% by adding appropriate amount of solvent or resin.

[0024] Preferably, the leveling agent is an organosilicon leveling agent, and the anti-settling agent is fumed silica.

[0025] Preferably, the prepared aluminum-silver paste can form a floating aluminum-silver paste or a non-leafing aluminum-silver paste.

[0026] Due to the adoption of the above process, the beneficial effects of the present invention are:

[0027] (1) The present invention achieves precise control of the particle size of aluminum-silver paste by optimizing the process parameters of various links such as raw material pretreatment, aluminum powder preparation, mixing and dispersion, and tempering and stabilization. Aluminum-silver paste products with different particle size ranges can be prepared according to different application requirements, thereby improving the applicability of the product.

[0028] (2) The present invention performs surface treatment on aluminum powder, which effectively enhances the dispersibility and corrosion resistance of the aluminum powder. At the same time, suitable additives are added during the mixing, dispersion and tempering stabilization process to improve the storage stability, leveling and anti-settling properties of the aluminum-silver paste, thereby improving the overall performance of the product.

[0029] (3) The present invention reduces the safety risks in the production process and ensures the safe production; and by reasonably controlling the process parameters, it reduces energy consumption to a certain extent. DETAILED DESCRIPTION

[0030] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0031] Example 1

[0032] A process for preparing a floating aluminum-silver paste with controllable particle size comprises the following steps:

[0033] (1) Raw material pretreatment

[0034] ① Select 100 kg of aluminum ingots with a purity of 99.8%, place them in a sodium hydroxide solution with a concentration of 8%, soak them at 50°C for 15 minutes to remove surface oxides and impurities, then rinse them repeatedly with deionized water until neutral, and dry them in a drying oven at 80°C for 2 hours to obtain the pretreated aluminum ingots;

[0035] ② The pretreated aluminum ingot was crushed into small pieces and placed in a reactor. 2.5 kg of stearic acid was added as a coating agent, and 200 kg of toluene was added as an organic solvent. The mixture was reacted at 70 ° C and a stirring speed of 400 rpm for 2 hours to uniformly coat the aluminum powder with stearic acid to enhance its hydrophobicity.

[0036] (2) Aluminum powder preparation

[0037] ①Put the pretreated aluminum block into the jaw crusher for initial crushing to a particle size of 3mm;

[0038] ② Transfer the coarsely crushed aluminum particles to a ball mill with a ball-to-powder ratio of 10:1. Use 5mm diameter zirconia balls as the grinding medium and grind under nitrogen. Control the ball mill speed to 300 rpm, aiming for an aluminum powder with a particle size of 8μm, and set the grinding time to 8 hours.

[0039] ③ Use an airflow classifier to classify the ground aluminum powder, adjust the airflow speed to 20m / s, the sorting temperature to 30℃, and collect aluminum powder that meets the particle size requirement of 8μm;

[0040] (3) Mixing and dispersion

[0041] ① Add 40kg xylene and 60kg alkyd resin into a planetary mixer and mix at a stirring speed of 300 rpm for 1.5 hours to fully dissolve and mix the two;

[0042] ② Add 40kg of the prepared aluminum powder to the mixed solvent resin system, along with 1kg of BYK series dispersant. Transfer to a sand mill and grind the aluminum paste to a fineness of <20μm under high shear conditions for 3 hours at a grinding pressure of 0.5MPa and 0.5mm diameter glass beads.

[0043] (4) Tempering and stabilization

[0044] ① Add 0.6kg of silicone leveling agent and 1.2kg of fumed silica to the dispersed aluminum-silver paste, and stir at a stirring speed of 200 rpm for 0.8 hours to evenly disperse the additives;

[0045] ② According to the spraying requirements, add an appropriate amount of xylene, adjust the viscosity of the aluminum-silver paste to 25 Pa·s, and adjust the solid content to 50% to obtain a floating aluminum-silver paste.

[0046] Example 2

[0047] A process for preparing a non-leafing aluminum-silver paste with controllable particle size comprises the following steps:

[0048] (1) Raw material pretreatment

[0049] ①Select 80kg of aluminum chips with a purity of 99.6%, put them into a 6% sodium hydroxide solution, soak them at 45℃ for 12 minutes, remove impurities, rinse with deionized water until neutral, and dry them in a drying oven at 75℃ for 2.5 hours;

[0050] ② Place the pretreated aluminum chips into a reactor, add 0.8 kg of silane coupling agent as a coating agent, and 150 kg of isopropyl alcohol as an organic solvent. The reaction is carried out at 65°C and a stirring speed of 350 rpm for 1.8 hours to evenly coat the aluminum powder with the silane coupling agent.

[0051] (2) Aluminum powder preparation

[0052] ① Use a jaw crusher to crush the aluminum chips to a particle size of about 4mm;

[0053] ② The coarsely crushed aluminum particles were transferred to a ball mill with a ball-to-powder ratio of 12:1, using 6mm diameter zirconia balls and grinding under argon protection. The ball mill speed was set to 350 rpm, with the goal of producing aluminum powder with a particle size of 12μm, and the grinding time was 5 hours. ③ The aluminum powder with a particle size of 12μm was collected using an airflow separator at an airflow speed of 18m / s and a separation temperature of 28°C.

[0054] (3) Mixing and dispersion

[0055] ① Add 50 kg of butyl acetate and 50 kg of acrylic resin into a planetary mixer and mix at a speed of 250 rpm for 1.2 hours;

[0056] ② Add 30kg of prepared aluminum powder, 0.8kg of BYK series dispersant, and 1kg of polyethylene glycol as a hydrophilic additive to the above system; transfer to a sand mill and grind at a grinding pressure of 0.6MPa and a grinding medium of 0.6mm diameter glass beads for 2.5 hours at high shear dispersion until the aluminum-silver paste has a fineness of less than 20μm;

[0057] (4) Tempering and stabilization

[0058] ① Add 0.5kg of silicone leveling agent and 1kg of fumed silica to the dispersed aluminum-silver paste and stir at a stirring speed of 180 rpm for 0.7 hours;

[0059] ② According to printing requirements, add an appropriate amount of resin, adjust the viscosity of the aluminum-silver paste to 35Pa·s, and adjust the solid content to 45% to obtain a non-leafing aluminum-silver paste.

[0060] The aluminum-silver pastes prepared in Example 1 and Example 2 are tested, and the results are as follows:

[0061]

[0062]

[0063] It can be seen from the above test data table that compared with traditional products, the leafing aluminum-silver paste of Example 1 has significantly improved mirror effect, corrosion resistance and storage stability; the non-leafing aluminum-silver paste of Example 2 is superior to traditional products in particle size control accuracy, dispersibility, corrosion resistance, metallic texture and storage stability.

[0064] The above description is only a preferred specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any technician familiar with the technical field, within the technical scope disclosed by the present invention, who makes equivalent replacements or changes based on the technical solution and inventive concept of the present invention, should be covered by the scope of protection of the present invention.

Claims

1. A process for preparing aluminum-silver paste with controllable particle size, characterized in that: The specific steps include: (1) Raw material pretreatment ① Select aluminum ingots or aluminum chips with a purity of not less than 99.5% as the raw material for preparing aluminum powder. Place the raw material in a sodium hydroxide solution with a concentration of 5% to 10%, soak it at 40-60℃ for 10 to 20 minutes to remove surface oxides and impurities, then rinse it repeatedly with deionized water until it is neutral, and dry it for later use; ② Place the pretreated aluminum powder in a reactor, add 0.3% to 3% of the coating agent by weight of the aluminum powder, and add an appropriate amount of organic solvent. React at 60-80°C and a stirring speed of 300-500 rpm for 1-3 hours to evenly coat the coating agent on the surface of the aluminum powder. (2) Aluminum powder preparation ①Put the pretreated aluminum raw materials into the jaw crusher for preliminary crushing, so that the particle size of the aluminum raw materials reaches 1-5mm; ② The coarsely crushed aluminum particles are transferred to a ball mill and ground under inert gas protection. The ball-to-material ratio in the ball mill is controlled at (5-15):1, and the grinding medium is zirconia balls with a diameter of 3-8 mm. During the grinding process, the speed of the ball mill is controlled at 200-400 rpm, and the grinding time is adjusted according to the target particle size. ③ Use an airflow separator to classify the ground aluminum powder. The airflow speed of the airflow separator is 10-30m / s and the separation temperature is 20-40℃. Aluminum powders of different particle sizes are separated and aluminum powders that meet the target particle size requirements are collected for later use. (3) Mixing and dispersion ① Add the organic solvent and the resin in a mass ratio of (3-7): (7-3) into a planetary mixer and mix them at a stirring speed of 200-400 rpm for 1-2 hours to fully dissolve and mix the organic solvent and the resin; ② Add the aluminum powder prepared in step (2) to the mixed solvent resin system, the amount of aluminum powder added is 20% to 40% of the total mass of the system, and at the same time add 0.5% to 2% of the total mass of the BYK series dispersant; then transfer the mixture to a sand mill, and perform high-speed shear dispersion under the conditions of a grinding pressure of 0.3-0.8 MPa and a grinding medium of glass beads with a diameter of 0.3-0.8 mm for 2-4 hours to fully disperse the aluminum powder in the system and grind until the fineness of the aluminum-silver paste reaches <20 μm.

2. The process for preparing aluminum-silver paste with controllable particle size according to claim 1, characterized in that: In step (1)②, the coating agent is stearic acid or a silane coupling agent.

3. The process for preparing aluminum-silver paste with controllable particle size according to claim 1, characterized in that: In step (2)②, when the target particle size is 1-5 μm, the grinding time is 12-24 hours; when the target particle size is 5-10 μm, the grinding time is 6-12 hours; when the target particle size is 10-20 μm, the grinding time is 3-6 hours.

4. The process for preparing aluminum-silver paste with controllable particle size according to claim 1, wherein: In step (3)①, the organic solvent is xylene or butyl acetate.

5. The process for preparing aluminum-silver paste with controllable particle size according to claim 1, characterized in that: In step (3)①, the resin is an alkyd resin or an acrylic resin.

6. The process for preparing aluminum-silver paste with controllable particle size according to claim 1, characterized in that: In step (3)②, a hydrophilic auxiliary agent is added as needed. The hydrophilic auxiliary agent is polyethylene glycol, and the addition amount is 0% to 2% of the total mass of the system.

7. A process for preparing aluminum-silver paste with controllable particle size according to any one of claims 1 to 6, characterized in that: The aluminum-silver paste prepared in step (3) is further tempered and stabilized as follows: ① Add 0.2% to 1% of the total mass of the leveling agent and 0.5% to 2% of the anti-settling agent to the dispersed aluminum-silver paste, and stir at a stirring speed of 100-300 rpm for 0.5-1 hour; ② Adjustment of viscosity and solid content: According to the application requirements of spraying or printing, adjust the viscosity of aluminum-silver paste to 10-50 Pa·s and the solid content to 40%-60% by adding appropriate amount of solvent or resin.

8. The process for preparing aluminum-silver paste with controllable particle size according to claim 7, characterized in that: The leveling agent is an organic silicone leveling agent and the anti-settling agent is fumed silica.

9. The process for preparing aluminum-silver paste with controllable particle size according to claim 8, characterized in that: The prepared aluminum-silver paste is divided into a floating aluminum-silver paste or a non-leafing aluminum-silver paste.

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